Home unsafe Home: Is air pollution in your house higher than outside?

Respiratory illnesses are on the rise due to rising air pollution in cities as well as rural areas.

But did you know that indoor air pollution is just as real as outside
air pollution?

According to a new study, people may be exposed to unhealthy levels of airborne pollutants inside their homes, even if the outdoor air quality is good.

Let’s take a closer look.

What does the study say?

The study published in Scientific Reports discovered that pollution levels at homes are higher and more variable than outdoor levels.

For two weeks, researchers at the University of Birmingham compared particulate matter (PM) in three homes using simple sensors and creative methods.

They discovered that the three houses had varying levels of PM, with one above the 24-hour PM2.5 limit set by the World Health Organization (WHO) on nine days.

Co-author and Clean Air Fellow Catrin Rathbone commented: “Our study shows the need to monitor indoor air pollution, as people can have unhealthy air at home even if outdoor air is good. PM levels varied significantly between homes, indicating that monitoring just one location isn’t enough.”

Also read: Is artificial rain the answer to Delhi’s air crisis?

What’s the reason?

To more precisely simulate indoor PM levels, researchers used Non-negative Matrix Factorisation (NMF), an effective technique for revealing latent patterns in data.

They were able to provide an enhanced view of the pollution levels within the houses by using inexpensive sensors.

The researchers note that the location of the home, ventilation, and occupancy patterns all had an impact on particle levels, indicating the complex nature of indoor air quality.

External factors such as the kitchen vent of a nearby restaurant also contribute to PM.

Additionally, they discovered that bigger particles (PM10) had a tendency to settle more quickly than smaller ones (PM1, PM2.5).

Co-author and Clean Air Fellow Owain Rose commented: “With more time spent working from home, understanding the factors that affect air quality within households is increasingly important. The methods we used accurately modelled indoor PM levels, helping to improve exposure estimates at a low cost.”

Also read: Delhi, Lahore, & Dhaka: Is South Asia becoming the world’s ‘smog capital’?

Similar study

One key product at home that has profound health implications for humans is indoor air fresheners.

While it doesn’t make much sense, as many of these products are used for aromatherapy, another study suggests it all contributes to indoor pollution.

The study claims using scented products indoors alters the chemistry of the air and contributes to air pollution equivalent to that of outside vehicle emissions.

Scented products, such as flame-free candles, are a significant source of nanosized particles. They are small enough to get deep into human lungs when inhaled and pose a potential risk to respiratory health.

According to researchers, inhaling these nanoparticles may have detrimental effects on one’s health.

The study by researchers at Purdue University was published in the journal Environmental Science and Technology Letters.

“A forest is a pristine environment, but if you’re using cleaning and aromatherapy products full of chemically manufactured scents to recreate a forest in your home, you’re actually creating a tremendous amount of indoor air pollution that you shouldn’t be breathing in,” study’s co-author Nusrat Jung, an assistant professor in Purdue’s Lyles School of Civil and Construction Engineering, said.

Researchers monitored these scented air fresheners in a small, mechanically ventilated test house, the Purdue Zero Energy Design Guidance for Engineers (zEDGE) lab, to determine the extent to which they can impact indoor air quality.

They began by measuring the nanoparticles that are produced when wax melts when heated.

The researchers found that melting wax produces a greater concentrated number of nanoparticles, especially those smaller than 100 nanometres (nm).

These levels are similar to the indoor pollution from gas stoves, diesel engines and even conventional candles.

Melting unscented waxes did not produce any discernible terpene emissions, suggesting that the aromatic nature of the melts is the primary driver of particle creation.

“Our research shows that fragranced products are not just passive sources of pleasant scents – they actively alter indoor air chemistry, leading to the formation of nanoparticles at concentrations that could have significant health implications,” said Jung, adding, “These processes should be considered in the design and operation of buildings and their HVAC [heating, ventilation, and air-conditioning] systems to reduce our exposures.”

With inputs from agencies